Manufacture of carbon molded bodies



Patented May 5, 1953 MANUFACTURE OF CARBON MOLDED BODIES Charle Desmond Greaves and William Duncan Parker, London, England, assignors to C. D. Patents Limited, London, England, a British company No Drawing. Application May 27, 1949, Serial No.

95,890. In Great Britain June 2, 1948 Claims.

This invention relates to improvements in the manufacture of carbon moulded bodies.

In United States specification No. 2,461,365, processes are described in which a moulded body ture at which the mixture will fiow, and the moulded shape is fired under non-oxidising conditions at a controlled rate of temperature rise such as to produce strong, tough, undistorted 2 products having no cellular structure visible to the naked eye.

As in the earlier processes above referred to, rapidity of temperature rise during firing tends made from finely divided bituminous coal alone 5 to promote strength and toughness in the fired or in conjunction with swell-inhibiting agents product but on the other hand rapidity of temis subjected under non-oxidising conditions to perature rise in that range of temperature witha firing operation at a carefully controlled rate in which gases or vapours may be generated in of temperature rise to produce strong, tough. unor evolved from the constituents of the moulded distorted products having no cellular structure composition (while that composition or a part visible to the naked eye, and in this specification of it is in a soft or semiliquid state) tends to the expression the type described refers to cause intumescence, and it is ,a feature of this the type of process in which such a carefully invention that the rate of temperature rise parselected rate of firing of a coal-containng mouldticularly within that temperature range whilst ed body is used to produce such products. being rapid is nevertheless insufilciently rapid The processes described in said earlier specifito cause swelling. cation were limited to the case where the coal Swell-inhibiting agents may also be employed used in the starting material had good aggluas described in United States specification No. tinating properties (e. g. had a swelling number of 2,461,365. 2-10). Again in said earlier processes the mate- Dealing now with the process in detail: rial subjected to the moulding was dry (1. e. it consisted of very finely divided coal alone or The raw materials compnse with a swell-inhibiting agent), and the mould- (a) cal'bonacequs coals or W115 Wlth ing pressures were generally high. The produc- 10 l5% Volatlle matter (on a dry ash'free tion of the strong, tough, undistorted products basis) having no cellular structure visible to the naked Plastlclsers' pltch tar or,coal'tar eye is a very striking phenomen which to a tillates (such as anthracene 011, naphtha or large extent is contributed to by the rate of firing -Pi Volatlle q of the moulded shapes, but there are certain cirta nmg compomlds i SO1- cumstances in which advantages accrue from Vents alone or f 1f f i g the use of plastic moulding compositions, i. e. (c) -Y l or cllemlcal swen'nflhiblfwrs as compositions in which the powdered coal before descnbed m Umted states Speclficatlon moulding into a desired shape is mixed with a hydrocarbon-containing plasticising agent aft- Commmutlon er which the firing of the type described takes (a) Coal Should be ground fi example mafia 100% to 100 mesh per linear inch and By this method it is possible to make large mesh Per hnear Inch finer if tiles, bowls and more complex shapes which cani m? not be so satisfactorily moulded from a dry (2)) Plast1c1s1ng agents such as pitch 1f solid powder 40 may be crushed to a convenient size for The hvdrocarbon-containing plasticising agents m z so as to pass through a to be mixed with the powdered coal may be solid 5 m Incl} Screen and/01. liquid they may be pitches tars, 3. Mixing is carried out at about IOU-150 C. or coal tar distillates (such as anthracene oil, napha that temperamre at which the plasticizer 'tha or benzene) or hydrocarbon-containing vola- 1S soft whl chever the highertile solvents singly or mixed. If solid, the plas- Mouldmg earned out at about 1000 or ticising agent is crushed to a particle size consomewhat hlgher' The pressure used may be venient for mixing g or less) relatively low (say about 2 tons per square This invention comprises a process of the type described for the manufacture of carbon moulded Drying It be deslliabls to heat the bodies in which process powdered coal is mixed moulfled shape pnor to firing m an oven at with one or more plasticising agents consisting 9 for some hours Over of or containing hydrocarbons of the kind specmght) m order to remove more Volatue ified, at an elevated temperature, the mixture q t is moulded to the desired Shape at a tempera 6.F1r1ng is earned out under non-oxidising conditions at a rapid rate of temperature rise conslstent with the avoidance of intumescence, swelling or cracking.

The pressing of the plastic composition may be automatic and a relatively low moulding pressure may be employed. so that the production of large moulded products (such as large tiles), is possible with smaller pressures than in the dry powder process described in the prior specifica tion above referred to.

Pressing rejects may be remixed and pressed again.

Example Per cent S. Wales carbonaceous coal having 14% volatile matter ground so that 90% passed through a 200 mesh sieve '80 Coal tar pitch (softening 105 C.-one-eighth inch mesh) 14 Naphthalene Oil (B. P. 255-290 C.) 6

These were mixed in a gas-heated, Z-blade mixer for 2 hours at 120-130 C. and then for the same time at 7075 C. to disintegrate any lumps. Bars were then moulded from the mix at a pressure of 2 tons per square inch in a mould at 100 C.

The moulded shapes were buried in ground coke in a steel box fitted with a lid and fired in a nonoxidising atmosphere at a rate of temperature rise of /2 C. per minute to 600 C. and then at a rate of temperature rise of 2 C. per minute to 1200 C., the latter temperature being maintained for 30 minutes. On cooling under non-oxidising conditions hard, strong, tough, undistorted products were obtained with the following characteristics:

Loss of weight 22.5 per cent Linear contraction 15.0 percent Apparent density 1.64 gin/cc. Porosity (to water) 8.4 per cent Modulus of rupture 8,200 lb./sq. in.

As mentioned above the mixture which is moulded may contain a swell-inhibiting agent of a diluent character such as a weakly-coking coal or a non-coking coal or pitch coke or coke breeze or graphite.

The determination of the rate of firing of the moulded articles is a matter of importance in the present invention. When the nature and proportions of the constituents of the mixture have been selected it is convenient to produce test-pieces from said mixture and to fire the test-pieces in a non-oxidising atmosphere to a temperature of at least 550 C. and to control the rate of firing in such manner as to produce a fired test-piece free from cracks and free from a cellular structure visible to the naked eye. Thereafter the moulded article according to this invention is fired under the conditions and at the rate at which the lastnamed test-piece was fired to produce an article having the properties of the last-named fired test-piece, and generally the moulded article thus fired is further fired to a temperature between 650 C. and 1200 C. to produce an article having freedom from cracks and cellular structure in like degree as said last-named fired test-piece, after which the fired article is cooled in a nonoxidising atmosphere.

We claim:

1. The process for the manufacture of carbon moulded bodies in whi h process powdered coal containing from 10 to per cent of volatile matter on a dry ash-free basis is intimately mixed and agitated at a temperature between 100 C. and 150 C. with a hydrocarbon-containing plasticizing agent which is plastic at that temperature, the proportions by weight being about 4 parts of coal to 1 part of plasticizing agent, the resulting mixture in a plastic condition is moulded to the desired shape at about the same temperature and under a pressure of the order of two tons per square inch and the moulded shape is then fired under non-oxidising conditions at a rate of temperature rise such as to produce an undistorted product free from cracks and having no cellular structure visible to the naked eye, the fired product being allowed to cool in a non-oxidising atmosphere.

2. The process for the manufacture of carbon moulded bodies in which process powdered coal containing from 10 to 15 per cent of volatile matter on a dry ash-free basis is intimately mixed and agitated for at least two hours at a temperature between 100 C. and 150 C. with a hydrocarbon-containing plasticizing agent which is plastic at that temperature, the proportions by weight being about 4 parts of coal to 1 part of plasticizing agent, the resulting mixture in a plastic condition is moulded to the desired shape at about the same temperature and under a pressure of the order of two tons per square inch and the moulded shape is then fired under non-oxidising conditions at a low rate of temperature rise of about C. per minute up to about 600 C. then at a higher rate of about 2 C. per minute up to about 1200 C., the fired product being allowed to cool in a non-oxidising atmosphere.

3. The process as claimed in claim 2 in which the coal is of a size which passes a sieve of 100 meshes to the linear inch.

4. The process as claimed in claim 2 in which the moulded shape, prior to firing, is dried at a temperature between 60 C. and 100 C. for some hours.

5. The process for the manufacture of carbon moulded bodies in which process powdered coal of which per cent passes a sieve of 200 meshes to the linear inch and which contains from 10 to 15 per cent of volatile matter on a dry ash-free basis is intimately mixed and agitated for at least two hours at a temperature between C. and C. with coal tar pitch ground to a particle size of about one-eighth of an inch and softening at a temperature of about 100 C. and with a hydrocarbon oil in the proportions, coal about 80 per cent, pitch about 14 per cent and hydrocarbon oil about 6 per cent, the resulting plastic mixture is moulded to the desired shape at about 100 C. and under a pressure of about 2 tons per square inch and the moulded shape is then buried in ground coke and fired in a non-oxidising atmosphere first at a rate of temperature rise of C. per minute to 600 C. and then at a rate of temperature rise of 2 C. per minute to 1200 C., the latter temperature being maintained for about 30 minutes before allowing the fired product to cool in a non-oxidising atmosphere.

CHARLES DESMOND GREAVES. WILLIAM DUNCAN PARKER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,304,773 Anderton Dec. 15, 1942 2,404,208 Bangham et a1. July 16, 1946 2,461,365 Bennett et al Feb. 8, 1949 2,466,435 Jones et a1. Apr. 5, 1949 

1. THE PROCESS FOR THE MANUFACTURE OF CARBON MOULDED BODIES IN WIHCH PROCESS POWDERED COAL CONTAINING FROM 10 TO 15 PER CENT OF VOLATILE MATTER ON A DRY ASH-FREE BASIS IS INTIMATELY MIXED AND AGITATED AT A TEMPERATURE BETWEEN 100* C. AND 150* C. WITH A HYDROCARBON-CONTAINING PLASTICIZING AGENT WHICH IS PLASTIC AT THAT TEMPERATURE, THE PROPORTIONS BY WEIGHT BEING ABOUT 4 PARTS OF COAL TO 1 PART OF PLASTICIZING AGENT, THE RESULTING MIXTURE IN A PLASTIC CONDITION IS MOULDED TO THE DESIRED SHAPE AT ABOUT THE SAME TEMPERATURE AND UNDER A PRESSURE OF THE ORDER OF TWO TONS PER SUQARE INCH AND THE MOULDED SHAPE IS THEN FIRED UNDER NON-OXIDISING CONDITIONS AT A RATE OF TEMPERATURE RISE SUCH AS TO PRODUCE AN UNDISTORTED PRODUCT FREE FROM CRACKS AND HAVING NO CELLULAR STRUCTURE VISIBLE TO THE NAKED EYE, THE FIRED PRODUCT BEING ALLOWED TO COOL IN A NON-OXIDISING ATMOSPHERE. 